1. Field of the Invention
The present invention relates to high-frequency switches, particularly to a high-frequency switch that can be used with a plurality of different mobile communication systems.
2. Description of the Related Art
As an existing high-frequency switch of this type, as shown in FIG. 5, a high-frequency switch described in Japanese Unexamined Patent Application Publication No. 2000-223901 (Patent Document 1) includes a first diode D11 and a second diode D12, the first diode D11 being series-connected to a signal path between an antenna terminal ANT and a transmission-side input terminal Tx, and the second diode D12 being shunt-connected to a signal path between the antenna terminal ANT and a reception-side output terminal Rx, and selective switching is performed between the signal path between the antenna terminal ANT and the transmission-side input terminal Tx and the signal path between the antenna terminal ANT and the reception-side output terminal Rx.
The amount of charges accumulated in diodes have variations on the order of ±10% even when the diodes are picked up arbitrarily from the same manufacturing lot. This causes a problem that switching from a transmission mode to a reception mode takes as long as 1 μs or longer in the high-frequency switch.
That is, in the transmission mode, the first and second diodes D11 and D12 are in the ON states, so that charges Q1 are accumulated in the first diode D11 and charges Q2 are accumulated in the second diode D12. Then, when a control power supply terminal Vc is set to 0 V in order to switch from the transmission mode to the reception mode, the charges accumulated in the first and second diodes D11 and D12 are mutually discharged. At this time, when Q1>Q2, the second diode D12 is quickly switched OFF, but it takes a certain time for the charges Q1 to become 0 so that the first diode D11 switches OFF substantially slower than the second diode D12. Thus, in the high-frequency switch, quick switching from the transmission mode to the reception mode is not enabled, so that a transmission signal having a large power leaks to a reception-side signal path.